Persons with severe mental illness (SMI) carry a tremendous burden of medical comorbid illness and die at least 10 years earlier than the U.S. population due in large part to early cardiovascular death. Regular physical activity decreases cardiovascular disease risk and improves longevity independent of weight or weight loss, yet effective interventions tailored to increase physical activity in persons with SMI are lacking. Social support positively influences physical activity in the general population, and peer support interventions are successful in health behavior change to prevent HIV. Hence, peer-supported physical activity may be an effective strategy to decrease cardiovascular risk in persons with SMI. The objective of this R34 application is to design and test a culturally appropriate physical activity intervention based in a peer-support model for persons with SMI in an urban community psychiatry program. We will adapt the peer support model from the HIV prevention peer outreach Self Help in Eliminating Lethal Disease Study. We propose the following Specific Aims: 1) Design a physical activity intervention emphasizing peer-support for persons with SMI in community psychiatry; 2) Conduct a randomized controlled study that tests the preliminary efficacy of the peer-supported physical activity intervention; 3) Evaluate the peer educators' experiences and compare peer educators' outcomes to participant outcomes; and 4) Use data from this pilot study to develop an R-01 proposal for a full-scale randomized controlled trial. We will recruit and train 20 peer educators to deliver the peer-supported physical activity (PS+PA) intervention. 40 participants will receive the physical activity intervention with peer-support (PS+PA) and will be compared to 40 receiving the same physical activity (PA) intervention without peer-support. All participants receive the PA intervention, providing group exercise classes and supervised open-gym hours for individual exercise. In the (PS+PA) arm, peer-educators will provide emotional, informational, instrumental and appraisal support to motivate subjects to participate in exercise. The primary outcome at 4 months will be cardiorespiratory fitness measured by heart rate response to submaximal treadmill test. Secondary outcomes will be: a): moderate physical activity measured by accelerometry; b) waist circumference; c) weight; d) health status; and e) depression symptom level. Process outcomes will be: a) self-efficacy and b) participation. This innovative proposal will use behavioral change methods successful in HIV prevention to design and test a peer-supported physical activity intervention in community psychiatry. We believe peer support will provide a novel and effective model for increasing physical activity in SMI. This study will provide important data for future work to reduce cardiovascular risk and improve health in persons with SMI. [unreadable] [unreadable] [unreadable]